This invention relates generally to improvements in the field of high pressure liquid connectors and more specifically to high pressure liquid connectors for use in high pressure liquid chromatography (HPLC) applications.
HPLC columns are produced by a number of different manufacturers. While there are some standard design considerations, HPLC manufacturers employ unique design specifications and techniques resulting in HPLC columns having proprietary parts. Of particular interest in the present invention are the proprietary end fittings of HPLC columns. Each of the columns utilizes an end fitting or end cap. The proprietary end fittings have different ferrule and tube stop lengths. Since each manufacturer uses proprietary end fittings there exists the problem that between the end fitting and the portion of the column containing the filter bed a dead volume can exist. The dead volume refers to the liquid space between the end of the liquid input line and the portion of the column containing the filter bed. Any amount of dead volume reduces the effectiveness of the column, wastes a portion of the liquid sample and could even be hazardous if this dead volume of liquid is spilled when the column is removed from the system or otherwise opened. To eliminate the dead volume, tubing is provided. The tubing provides a path through which the sample is made to flow. The tubing is made to intimately contact an inlet and outlet portion of the column containing the filter bed in a liquid-tight fitting, thereby hopefully eliminating any dead space where liquid can collect. The difficulty associated with trying to eliminate or at least reduce the dead volume in this manner is that each proprietary column requires a different length of tubing in order to bottom out against the column end due to the different ferrule and tubing stop lengths.
As the column is assembled, the tubing of a connector is pushed into the end fitting as far as possible thereby contacting the column end. Technicians and others assembling HPLC columns must individually gauge how far to insert the end cap connector tubing into the HPLC column end fitting. Oftentimes the tubing is crimped or otherwise distorted when the end cap connector is fully tightened. This compromises the tubing and leads to accumulation of fluid or malfunctioning of the column instead of eliminating a dead volume as desired.
The apparatus of the present invention is a universal high pressure liquid connector, which automatically accommodates differing ferrule depths, and tube stops of proprietary HPLC column end fittings thereby reducing and eliminating the potential dead volume and or leaks in mating connections. The present invention employs an internal spring-loaded mechanism that maintains sufficient pressure in the critical area of the connection once the universal high pressure liquid connector of the present invention and the HPLC column fitting have engaged. The critical area of the connection being where the end of the universal high pressure liquid connector mating tubing bottoms out on the internal female fitting and the ferrule of the mating connection seats within the geometry of the mating port connection of the HPLC column. If an incorrect connection is made, i.e. the tubing does not bottom out, and or the ferrule seats improperly, a dead volume is created resulting in poor chromatographic performance or a leak path is created.
It is therefore an objective of the present invention to provide a high pressure liquid connector for use in HPLC columns having universal compatibility. Since there are a variety of industry standard port depths relating to HPLC column female fitting geometry, the apparatus of the present invention is designed to accommodate all port depths. Similar to a finger-tight fitting, the apparatus of the present invention does not have a fixed ferrule. Instead, the ferrule has the ability to freely slide up and down the connecting tubing, allowing the apparatus of the present invention to adjust to any port depth. Unlike finger tight fittings however, one using the present invention does not have to maintain pressure on the tubing to ensure a zero dead volume connection. The internal spring-loaded mechanism ensures the zero dead volume connection by maintaining pressure on the tubing into the bottom of the female port. Therefore, regardless of the port depth, the universal high pressure liquid connector of the present invention will always guarantee a zero dead volume connection.
Furthermore, the apparatus of the present invention requires no wrenches or other special tools to make a liquid-tight sealed connection with a HPLC column end fitting. It is important to note that the present invention is stable to 6000 pounds per square inch (psi).
The sliding ferrule-to-capillary tube configuration of the present invention is better than previous connectors having fixed ferrule fitting configurations in a number of ways. First, fixed ferrule fittings are not universal. Normally, once the ferrule has been swaged to the capillary tube in a fixed ferrule connector apparatus, the connector can only be used with a female fitting having an exact matching port depth. Furthermore, it has been observed that female port depths vary even within the same batch of fittings from the same supplier alleging to be made to the same specifications. Therefore, unless a connector having a fixed ferrule fitting is swaged when changing connections from one fitting to the next, a zero dead volume and leak free connection cannot be guaranteed.
Secondly, connectors having fixed ferrule fittings typically require wrenches to make the connection. The universal high pressure liquid connector of the present invention incorporates a finger tight engagement means, which does not require the use of wrenches or other tools in order to effectuate a leak proof mating connection.
Thirdly, the fixed ferrule fittings of previous designs can deform the connecting tubing. By overswaging the fitting onto the capillary tubing, the tubing may be crimped, thereby causing a deformity on the inner wall of the connector capillary tubing, which can lead to poor chromatographic performance.
The apparatus of the present invention is better than traditional finger tight fittings in a number of aspects. First, traditional finger tight fittings require the technician to maintain pressure on the tubing into the female port to ensure a zero dead volume connection. Operator error and or ignorance may, and does, lead to improper connection techniques wherein the end of the capillary tube of the connector does not properly bottom out on the mating female fitting, thus introducing a dead volume and potential leakpaths. The apparatus of the present invention however applies constant pressure on the connector tubing inserted into the female port via the internal spring-loaded mechanism, thereby greatly reducing the potential for operator error.
Secondly, since a technician must maintain pressure on the tubing while making a connection, and different technicians use different hand positions to do so, the connector tubing may become bent in many ways. When the tubing becomes bent in the last 1-2 centimeters where the finger-tight fitting is located, a leak may occur, thus rendering the tubing useless and requiring replacement of the capillary tubing and possibly the finger tight fitting as well since the bent capillary tubing may have deformed the finger tight fitting.
Thirdly, most finger tight fittings use a polymeric male thread that degrades after repeated connections. The male polymeric threads will degrade to a point where they will no longer ensure a positive connection thus rendering the finger tight fitting no longer useable. The finger tight connection then requires replacement. The preferred embodiment of the present universal self-adjusting high pressure liquid connector typically has a stainless steel male thread sold under the name of NITRONIC-60 located on the exterior of the connector""s stem for threadedly engaging with a HPLC column. Yet another version of the present invention would further comprise male threads constructed of an anti-gall material by Carpenter Technology, Inc under the name of GALL-TOUGH. However any other material with similar properties that will not degrade and will not gall due to its metallurgic properties is appropriate and contemplated within the scope of the present invention.
The present invention offers additional benefits not realized from using traditional stainless steel finger tight fittings. Traditional adjustable stainless steel fittings require the technician to maintain pressure on the tubing into the female port to ensure a zero dead volume connection. Additionally, these stainless fittings require the technician to push the ferrule up the tubing to expose enough tubing beyond the ferrule to ensure a zero dead volume connection each time the traditional adjustable connector is used. The universal self-adjusting high pressure liquid connector of the present invention however applies a self-adjusting pressure on the capillary tubing inserted into the female port via the internal spring-loaded mechanism each time the universal self-adjusting high pressure liquid connector is used.
Secondly, most traditional adjustable stainless fittings use a stainless steel male thread, which after repeated connections will degrade. The stainless steel threads will degrade to a point where they will have a tendency to gall and will no longer be useable requiring replacement. The universal self-adjusting high pressure liquid connector, as discussed above, typically has a stainless steel male thread that will not degrade and will not gall due to its metallurgic properties.
Other design applications for the present invention include the incorporation of the connection device into a hand tight cartridge style column and guard column system. The Isolation Technologies, Inc. product known under the trademark QUICKSEAL analytical cartridge system is being modified to include the apparatus connector at the inlet and outlet ends of columns as short as 1 cm in length with no restrictions on column lengths. Column system inner diameters may range from 1.0 millimeters (mm) to 10.0 mm, however these ranges certainly pose no restriction but do show the advantages that the apparatus can bring to the industry.
As such, it is an object of the present invention to provide an universal self-adjusting high pressure liquid connector designed for fluid transfer applications capable of self-adjusting, hand tight connection thereby eliminating the potential for improper connections due to variance in mating fitting geometry.
Another object of the present invention is to provide an apparatus that lends itself to both high and low pressure applications, i.e. those applications involving pressures both above and below 6000 psi.
It is further an object of the present invention to provide an apparatus which is chemically inert.
These and other objects of the present invention will become more readily apparent from the detailed description given hereafter. However, it should be understood that a detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this description.